Device for providing reverse heating and method of reverse heating

ABSTRACT

A method of reverse heating using intermittent temperature zones at normal pressure, including: 1) introducing hydrothermal water or steam to a heating coil inside intermittent temperature zones of cabinets of a heating device via a duct along a first direction; 2) introducing combusted high temperature flue gas to a hydrothermal radiation coil inside the cabinets of the heating device via a gas duct along a second direction which is a reverse direction of the first direction; and 3) at normal pressure, heating the hydrothermal water or steam by the flue gas and a heat transfer medium inside the cabinets of the heating device. A heating device for use in the method is also provided. The method and device feature high thermal efficiency at low cost.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent Application No. PCT/CN2009/000664 with an international filing date of Jun. 18, 2009, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 200910143170.4 filed May 19, 2009. The contents of all of the aforementioned applications, including any intervening amendments thereto, are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method of reverse heating using intermittent temperature zones at normal pressure, and more particularly to a heating device for comprehensive utilization of recovered waste heat from a furnace.

2. Description of the Related Art

Conventional furnaces have high exhaust temperature at approx. 250-375° C., and the exhaust vents extend out of the furnaces, heat energy contained in the flue gas and steam with higher calorific value is directly discharged to the air, resulting in energy loss and pollution. To recycle the high temperature waste heat, reduce exhaust temperature, and increase heat transfer efficiency of furnaces, a method of reverse heating using intermittent temperature zones at normal pressure and a device related thereto are provided herein.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of the invention to provide a method of reverse heating using intermittent temperature zones at normal pressure. The method relates to a waste heat utilization technology.

It is another objective of the invention to provide a heating device for comprehensive utilization of recovered waste heat from a furnace.

To achieve the above objectives, in accordance with one embodiment of the invention, there is provided a method of reverse heating using intermittent temperature zones at normal pressure, the method comprising the following steps:

1) Introducing hydrothermal water or steam to a heating coil inside intermittent temperature zones of cabinets of a heating device via a duct along a first direction;

2) Introducing combusted high temperature flue gas to a hydrothermal radiation coil inside the cabinets of the heating device via a gas duct along a second direction which is a reverse direction of the first direction; and

3) At normal pressure, heating the hydrothermal water or steam by the flue gas and a heat transfer medium inside the cabinets of the heating device.

In a class of this embodiment, the intermittent temperature zones refer to intermittent or independent temperature zones, created inside the cabinets of the heating device due to varied heat transfer medium therein; the heating device comprises a plurality of series-connected cabinets and two adjacent cabinets are connected.

In a class of this embodiment, the reverse direction means that the flue gas enters from the top of the cabinets and heat energy is transferred by radiation from top to bottom through the hydrothermal radiation coil; the hydrothermal water or steam enters from the bottom of the cabinets and flows from bottom to top through the heating coil. The hydrothermal radiation coil exchanges heat energy with the heat transfer medium and the hydrothermal water or steam downstream and the hydrothermal water or steam and flue gas flow in a reverse direction.

In a class of this embodiment, the normal pressure means that the pressure is to be released via an overflow pipe when the pressure inside the cabinets exceeds the normal pressure and the heat transfer medium discharged during the pressure relief is collected by a waste box via a discharge pipe.

In a class of this embodiment, the heat transfer medium comprises fluid such as water, oil, sodium, lithium, mercury, and fused salt.

In accordance with another embodiment of the invention, there provided is a heating device comprising intermittent temperature zones for comprehensive utilization of recovered waste heat at normal pressure, the heating device comprising a plurality of cabinets, a flue gas cyclic heating circuit, a hydrothermal water or steam cyclic heating duct, and a control system, wherein the flue gas cyclic heating circuit and the hydrothermal water or steam cyclic heating duct flow in a reverse direction.

In a class of this embodiment, the cabinets are in a shape of square, rectangle, cylinder, or elliptic cylinder, with an upper end of each of the cabinets arranged with an overflow pipe. The hydrothermal radiation coil and the heating coil are arranged in parallel and distributed evenly in reticulation inside the cabinets.

In a class of this embodiment, the flue gas cyclic heating circuit is in an enclosed annular structure comprising a heat generator, the hydrothermal radiation coil, a waste heat exchanger, a coil heat exchange pipe, an air intake fan, and a gas mixture supply duct.

In a class of this embodiment, the hydrothermal water or steam cyclic heating duct is in an enclosed annular structure comprising a duct, the heating coil, a duct exit, a heat receiver, and a check valve.

In a class of this embodiment, a temperature detector connecting with a temperature controller is arranged inside each of the cabinets.

High temperature flue gas produced by the heat generator passes through the hydrothermal radiation coil in different temperature zones to transfer heat energy to the heat transfer medium inside the cabinets by radiation. When different hydrothermal water or steam passing through the heating coil reaches to a desired temperature, the flue gas and part of hydrothermal water or steam having higher calorific value discharged conventionally will be recycled by the waste heat exchanger.

The top of the cabinet is arranged with the overflow pipe connecting to the air but without air pressure produced, which ensures safe operation of the whole system. From the manufacturing perspective, it is a heating device with normal pressure. Thus, the manufacturing level and metal consumption is reduced, energy is saved, and dust/fume discharge is decreased.

Advantages of the invention are summarized below:

1) The more temperature zones are divided, the higher the thermal efficiency;

2) Large amount of energy is saved and production costs reduced; and

3) The device generates no pressure and is different from a pressure vessel, with low investment and zero risk.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described hereinbelow with reference to accompanying drawings, in which the sole FIGURE is a schematic diagram of a heating device in accordance with one embodiment of the invention.

In the drawings, the following reference numbers are used:

1—Fuel gas supply duct, 2—Heat generator, 3—Gas mixture supply duct, 4—Gas duct, 5—Duct exit, 6—Duct, 7—Check valve, 8—Air intake fan, 9—Detector, 10—Hydrothermal radiation coil, 11—Heating coil, 12—Cabinet, 13—Heat transfer medium, 14—Waste heat exchanger, 15—Overflow pipe, 16—Coil heat exchange pipe, 17—Exhaust fan, 18—Waste box, 19—Temperature controller, 20—Heat receiver.

DETAILED DESCRIPTION OF THE EMBODIMENTS

As shown in the sole FIGURE, a method of reverse heating using intermittent temperature zones at normal pressure provided by the invention comprises the following steps:

1) Introducing hydrothermal water or steam to a heating coil 11 inside intermittent temperature zones of cabinets 12 of a heating device via a duct 6 along a first direction;

2) Introducing combusted high temperature flue gas to a hydrothermal radiation coil 10 inside the cabinets 12 of the heating device via a gas duct 4 along a second direction which is a reverse direction of the first direction; and

3) At normal pressure, heating the hydrothermal water or steam by the flue gas and a heat transfer medium 13 inside the cabinets 12 of the heating device.

The intermittent temperature zones refer to intermittent or independent temperature zones, created inside the cabinets 12 of the heating device due to varied heat transfer medium 13 therein. The heating device comprises a plurality of series-connected cabinets 12 and two adjacent cabinets 12 are connected.

The reverse direction means that the flue gas enters from the top of the cabinets 12 of the heating device and heat energy is transferred by radiation from top to bottom through the hydrothermal radiation coil 10; the hydrothermal water or steam enters from the bottom of the cabinets 12 and flows from bottom to top through the heating coil 11. The hydrothermal radiation coil 10 exchanges heat energy with the heat transfer medium 13 and the hydrothermal water or steam in a downstream mode and the hydrothermal water or steam and flue gas flow in a reverse direction.

The normal pressure means that the pressure is to be released via an overflow pipe 15 when the pressure inside the cabinets 12 exceeds the normal pressure and the heat transfer medium 13 discharged during the pressure relief is collected by a waste box 18 via a discharge pipe.

The heat transfer medium 13 comprises fluid such as water, oil, sodium, lithium, mercury, and fused salt.

A heating device comprising intermittent temperature zones for comprehensive utilization of recovered waste heat at normal pressure, comprises a plurality of cabinets, a flue gas cyclic heating circuit, a hydrothermal water or steam cyclic heating duct, and a control system, wherein the flue gas cyclic heating circuit and the hydrothermal water or steam cyclic heating duct flow in a reverse direction.

The cabinets 12 are in a shape of square, rectangle, cylinder, or elliptic cylinder, with an upper end of each of the cabinets arranged with an overflow pipe 15. A hydrothermal radiation coil 10 and a heating coil 11 are arranged in parallel and distributed evenly in reticulation inside the cabinets 12.

The flue gas cyclic heating circuit is in an enclosed annular structure comprising a heat generator 2, the hydrothermal radiation coil 10, a waste heat exchanger 14, a coil heat exchange pipe 16, an air intake fan 8, and a gas mixture supply duct 3.

The hydrothermal water or steam cyclic heating duct is in an enclosed annular structure comprising a duct 6, the heating coil 11, a duct exit 5, a heat receiver 20, and a check valve 7.

A temperature detector 9 connecting with a temperature controller 19 is arranged inside each of the cabinets 12. When the detector 9 is located between the hydrothermal radiation coil 10 and the heating coil 11 of the cabinets 12, it has a more accurate temperature detection capability.

High temperature flue gas produced by the heat generator 2 passes through the hydrothermal radiation coil 10 in different temperature zones to transfer heat energy to the heat transfer medium 13 inside the cabinets 12 by radiation. When different hydrothermal water or steam passing through the heating coil 11 reaches to a desired temperature, the flue gas and part of hydrothermal water or steam having higher calorific value but discharged conventionally will be recycled by the waste heat exchanger 14.

After fuel gas enters the heat generator 2 via a fuel gas supply duct 1 and combusts with the air mixture inside the heat generator 2, a high temperature flue gas is produced and washes the inner wall of the hydrothermal radiation coil 10 with a high flow rate and thus heat energy is radiated through the hydrothermal radiation coil 10. The temperature of the heat transfer medium 13 at the temperature zone of a cabinet 12 rises quickly due to the heat radiation of the hydrothermal radiation coil 10. The detector 9 measures the temperature. When the temperature reaches to a preset temperature of the temperature controller 19, an inlet valve of the duct 6 is opened and by an external force (e.g. a pump) the hydrothermal water or steam is driven to flow inside the heating coil 11 in a reverse direction compared with the flue gas.

Since the flue gas flows inside the connected hydrothermal radiation coil 10, when the flue gas flows to the temperature zone of a next cabinet 12, the heat transfer medium 13 therein will acquire higher quantity of heat due to heat release and heat transfer. After the temperature rises to a preset temperature of the temperature controller 19, heat will be transferred to the temperature zone of a further next cabinet 12. After passing through a plurality of cabinets 12, the remaining flue gas having higher calorific value enters the waste heat exchanger 14 comprising the coil heat exchange pipe 16. Heat energy exchanges in the coil heat exchange pipe 16. Thereafter, the flue gas is mixed with fresh air again and enters the heat generator 2 via a gas mixture supply duct 3 and combusts again with fuel gas. With respect to the temperature gradient, the method and device of reverse heating increases the furnace temperature and improves fire condition and combustion process and thus further improves the combustion efficiency and heat transfer effect. Thus, an enclosed annular structure of the flue gas cyclic heating circuit comprising the heat generator 2, the hydrothermal radiation coil 10, the waste heat exchanger 14, the coil heat exchange pipe 16, the air intake fan 8, and the gas mixture supply duct 3 is formed to heat the hydrothermal water or steam inside the heating coil 11 and meanwhile speed up the flow rate thereof inside the heating coil 11.

The temperature controller 19 controls the heat produced by combustion of the heat generator 2. By means of heat transfer of the hydrothermal radiation coil 10 and circulation of the waste heat exchanger 14, the flue gas and hydrothermal water or steam having higher calorific value can be effectively controlled to form different temperature zones for heating the fluid requiring for different temperature, and meanwhile energy is saved, dust/fume discharge is reduced.

The top of the cabinet 12 is arranged with the overflow pipe 15 connecting to the air. To ensure safe operation of the whole system, when inner pressure of the cabinet 12 exceeds the normal pressure, pressure is released via the overflow pipe 15 and the heat transfer medium 13 discharged therewith is collected by the waste box 18 through a discharge pipe. From the manufacturing perspective, it is a heating device with normal pressure; therefore manufacturing level and metal consumption is reduced.

The end of the waste heat exchanger 14 is mounted with an exhaust fan 17, which deposits the dust and fume passing through the inner tube of the waste heat exchanger and quickly discharges them outside. Exhaust temperature at the opening of the waste heat exchanger shall be controlled to have a temperature difference of within 30° C. with the ambient temperature so as to reach the lowest gas exhaust temperature and complete the utilization of the steam enthalpy.

To increase temperature of the heat receiver, one or more cabinets 12 can be added, in which different types of heat transfer mediums 13 are arranged. In the presence of the different types of heat transfer mediums 13, the hydrothermal radiation coil 10 will transfer heat to the heat transfer mediums inside the cabinets 12 to create different temperature zones, thereby forming a high-temperature steam.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the invention. 

The invention claimed is:
 1. A method of reverse heating, the method comprising the steps of: a) introducing hydrothermal water or steam to a heating coil inside intermittent temperature zones of cabinets of a heating device via a duct along a first direction; b) introducing combusted flue gas to a hydrothermal radiation coil inside the cabinets of the heating device via a gas duct along a second direction which is a reverse direction of the first direction; and c) at normal pressure, heating the hydrothermal water or steam by the flue gas and a heat transfer medium inside the cabinets of the heating device.
 2. The method of claim 1, wherein the intermittent temperature zones refer to intermittent or independent temperature zones, created inside the cabinets of the heating device due to varied heat transfer medium therein; and the heating device comprises a plurality of series-connected cabinets and two adjacent cabinets are connected.
 3. The method of claim 1, wherein the reverse direction means that the flue gas enters from the top of the cabinets and heat energy is transferred by radiation from top to bottom through the hydrothermal radiation coil; the hydrothermal water or steam enters from the bottom of the cabinets and flows from bottom to top through the heating coil; and the hydrothermal radiation coil exchanges heat energy with the heat transfer medium and the hydrothermal water or steam downstream and the hydrothermal water or steam and flue gas flow in a reverse direction.
 4. The method of claim 1, wherein the normal pressure means that pressure is to be released via an overflow pipe when pressure inside the cabinets exceeds the normal pressure and the heat transfer medium discharged during the pressure relief is collected by a waste box via a discharge pipe.
 5. The method of claim 1, wherein the heat transfer medium is a fluid of water, oil, sodium, lithium, mercury, and fused salt.
 6. A heating device comprising intermittent temperature zones for comprehensive utilization of recovered waste heat at normal pressure, comprising: a) a plurality of cabinets; b) a flue gas cyclic heating circuit; c) a hydrothermal water or steam cyclic heating duct; and d) a control system; wherein the flue gas cyclic heating circuit and the hydrothermal water or steam cyclic heating duct flow in a reverse direction.
 7. The heating device of claim 6, wherein the cabinets are in a shape of square, rectangle, cylinder, or elliptic cylinder, with an upper end of each of the cabinets arranged with an overflow pipe, and the hydrothermal radiation coil and the heating coil are arranged in parallel and distributed evenly in reticulation inside the cabinets.
 8. The heating device of claim 6, wherein the flue gas cyclic heating circuit is in an enclosed annular structure comprising a heat generator, the hydrothermal radiation coil, a waste heat exchanger, a coil heat exchange pipe, an air intake fan, and a gas mixture supply duct.
 9. The heating device of claim 6, wherein the hydrothermal water or steam cyclic heating duct is in an enclosed annular structure comprising a duct, the heating coil, a duct exit, a heat receiver, and a check valve.
 10. The heating device of claim 6, wherein a temperature detector connecting with a temperature controller is arranged inside each of the cabinets.
 11. The heating device of claim 6, wherein the normal pressure means that pressure is to be released via an overflow pipe when pressure inside the cabinets exceeds the normal pressure. 